The Gegenschein over Chile

Is the night sky darkest in the direction opposite the Sun? No. In fact, a rarely discernable faint glow known as the gegenschein (German for "counter glow") can be seen 180 degrees around from the Sun in an extremely dark sky. The gegenschein is sunlight back-scattered off small interplanetary dust particles. These dust particles are millimeter sized splinters from asteroids and orbit in the ecliptic plane of the planets. In this picture from last year is one of the more spectacular pictures of the gegenschein yet taken. Here a deep exposure of an extremely dark sky over Las Campanas Observatory in Chile shows the gegenschein so clearly that even a surrounding glow is visible. Notable background objects include the Andromeda Galaxy, the Pleiades star cluster, the California Nebula, the belt of Orion just below the Orion Nebula and inside Barnard's Loop, and bright stars Rigel and Betelgeuse. The gegenschein is distinguished from zodiacal light near the Sun by the high angle of reflection. During the day, a phenomenon similar to the gegenschein called the glory can be seen in reflecting air or clouds opposite the Sun from an airplane.

Image Credit & Copyright: Yuri Beletsky
Explanation from: http://apod.nasa.gov/apod/ap140114.html

The Shocking Behavior of a Speedy Star

Roguish runaway stars can have a big impact on their surroundings as they plunge through the Milky Way Galaxy. Their high-speed encounters shock the galaxy, creating arcs, as seen in this newly released image from NASA’s Spitzer Space Telescope.

In this case, the speedster star is known as Kappa Cassiopeiae, or HD 2905 to astronomers. It is a massive, hot supergiant moving at around 2.5 million mph relative to its neighbors (1,100 kilometers per second). But what really makes the star stand out in this image is the surrounding, streaky red glow of material in its path. Such structures are called bow shocks, and they can often be seen in front of the fastest, most massive stars in the galaxy.

Bow shocks form where the magnetic fields and wind of particles flowing off a star collide with the diffuse, and usually invisible, gas and dust that fill the space between stars. How these shocks light up tells astronomers about the conditions around the star and in space. Slow-moving stars like our sun have bow shocks that are nearly invisible at all wavelengths of light, but fast stars like Kappa Cassiopeiae create shocks that can be seen by Spitzer’s infrared detectors.

Incredibly, this shock is created about 4 light-years ahead of Kappa Cassiopeiae, showing what a sizable impact this star has on its surroundings. (This is about the same distance that we are from Proxima Centauri, the nearest star beyond the Sun.)

The Kappa Cassiopeiae bow shock shows up as a vividly red color. The faint green features in this image result from carbon molecules, called polycyclic aromatic hydrocarbons, in dust clouds along the line of sight that are illuminated by starlight.

Delicate red filaments run through this infrared nebula, crossing the bow shock. Some astronomers have suggested these filaments may be tracing out features of the magnetic field that runs throughout our galaxy. Since magnetic fields are completely invisible themselves, we rely on chance encounters like this to reveal a little of their structure as they interact with the surrounding dust and gas.

Kappa Cassiopeiae is visible to the naked eye in the Cassiopeia constellation (but its bow shock only shows up in infrared light.)

For this Spitzer image, infrared light at wavelengths of 3.6 and 4.5 microns is rendered in blue, 8.0 microns in green, and 24 microns in red.

Image Credit: NASA/JPL-Caltech
Explanation from: http://www.nasa.gov/jpl/spitzer/bow-shock-wave-20140220/

Aurora over Troms

Troms, Norway

Image Credit & Copyright: Tommy Richardsen

Comet Hale-Bopp seen over Indian Cove

Comet Hale-Bopp, the Great Comet of 1997, was quite a sight. In this photograph taken on 1997 April 6, Comet Hale-Bopp was imaged from the Indian Cove Campground in the Joshua Tree National Park in California, USA. A flashlight was used to momentarily illuminate foreground rocks in this six minute exposure. An impressive blue ion tail was visible above a sunlight-reflecting white dust tail. Comet Hale-Bopp remained visible to the unaided eye for over a year before returning to the outer Solar System and fading.

Image Credit & Copyright: Wally Pacholka
Explanation from: http://apod.nasa.gov/apod/ap131124.html

Geminid Meteors over Chile

From a radiant point in the constellation of the Twins, the annual Geminid meteor shower rained down on planet Earth in December 2013. Recorded near the shower's peak over the night of December 13 and 14, the above skyscape captures Gemini's shooting stars in a four-hour composite from the dark skies of the Las Campanas Observatory in Chile. In the foreground the 2.5-meter du Pont Telescope is visible as well as the 1-meter SWOPE telescope. The skies beyond the meteors are highlighted by Jupiter, seen as the bright spot near the image center, the central band of our Milky Way Galaxy, seen vertically on the image left, and the pinkish Orion Nebula on the far left. Dust swept up from the orbit of active asteroid 3200 Phaethon, Gemini's meteors enter the atmosphere traveling at about 22 kilometers per second.

Image Credit & Copyright: Yuri Beletsky
Explanation from: http://apod.nasa.gov/apod/ap131223.html

The Colorful Clouds of Rho Ophiuchi

The many spectacular colors of the Rho Ophiuchi clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the star Rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light. The Earth's daytime sky appears blue for the same reason. The red and yellow regions shine primarily because of emission from the nebula's atomic and molecular gas. Light from nearby blue stars - more energetic than the bright star Antares - knocks electrons away from the gas, which then shines when the electrons recombine with the gas. The dark brown regions are caused by dust grains - born in young stellar atmospheres - which effectively block light emitted behind them. The Rho Ophiuchi star clouds, well in front of the globular cluster M4 visible above on lower left, are even more colorful than humans can see - the clouds emits light in every wavelength band from the radio to the gamma-ray.

Image Credit & Copyright: Rafael Defavari
Explanation from: http://apod.nasa.gov/apod/ap131203.html

Lightning in Slow Motion (7,207 images per second)

How fast is lightning? Lightning, in fact, moves not only too fast for humans to see, but so fast that humans can't even tell which direction it is moving. This lightning stroke did not move too fast, however, for this extremely high time resolution video to resolve. Tracking at an incredible 7,207 frames per second, actual time can be seen progressing at the video bottom. This lightning bolt starts with many simultaneously creating ionized channels branching out from an negatively charged pool of electrons and ions that has somehow been created by drafts and collisions in a rain cloud. About 0.015 seconds after appearing - which takes about 3 seconds in this time-lapse video - one of the meandering charge leaders makes contact with a suddenly appearing positive spike moving up from the ground and an ionized channel of air is created that instantly acts like a wire. Immediately afterwards, this hot channel pulses with a tremendous amount of charges shooting back and forth between the cloud and the ground, creating a dangerous explosion that is later heard as thunder. Much remains unknown about lightning, however, including details of the mechanism that separates charges.

Video Credit & Copyright: Tom A. Warner
Explanation from: http://apod.nasa.gov/apod/ap120723.html

A Rainbow Pileus Cloud over Zimbabwe

Yes, but how many dark clouds have a multicolored lining? Pictured, behind this darker cloud, is a pileus iridescent cloud, a group of water droplets that have a uniformly similar size and so together diffract different colors of sunlight by different amounts. This image was taken just before sunset when it was noticed by chance by a photographer in Murambi East, near Odzi Valley and the Mtanda Range of Zimbabwe. Also captured were unusual cloud ripples above the pileus cloud. The formation of a rare pileus cloud capping a common cumulus cloud is an indication that the lower cloud is expanding upward and might well develop into a storm. In this case, however, only a few minutes after the colorful cloud was noticed, it disappeared.

Image Credit & Copyright: Peter Lowenstein
Explanation from: http://apod.nasa.gov/apod/ap140219.html

The Hubble Ultra Deep Field (HUDF) shows over 10 000 galaxies in a mere 0.000024% of the sky

Astronomers at the Space Telescope Science Institute today unveiled the deepest portrait of the visible universe ever achieved by humankind. Called the Hubble Ultra Deep Field (HUDF), the million-second-long exposure reveals the first galaxies to emerge from the so-called "dark ages," the time shortly after the big bang when the first stars reheated the cold, dark universe. The new image should offer new insights into what types of objects reheated the universe long ago.

This historic new view is actually two separate images taken by Hubble's Advanced Camera for Surveys (ACS) and the Near Infrared Camera and Multi-object Spectrometer (NICMOS). Both images reveal galaxies that are too faint to be seen by ground-based telescopes, or even in Hubble's previous faraway looks, called the Hubble Deep Fields (HDFs), taken in 1995 and 1998.

1. How faint are the farthest objects?
The Hubble observations detected objects as faint as 30th magnitude. The faintest objects the human eye can see are at sixth magnitude. Ground-based telescopes also can detect 30th-magnitude objects. Those objects, however, are so dim they are lost in the glare of brighter, nearby galaxies.

Searching for the faintest objects in the Ultra Deep Field is like trying to find a firefly on the Moon. Light from the farthest objects reached the Hubble telescope in trickles rather than gushers. The orbiting observatory collected one photon of light per minute from the dimmest objects. Normally, the telescope collects millions of photons per minute from nearby galaxies.


2. How many orbits did it take to make the observations?
It took 400 orbits to make the observations.


3. How many exposures were needed to make the observations?
The Hubble telescope's Advanced Camera for Surveys' wide-field camera snapped 800 exposures, which equals two exposures per orbit. The exposures were taken over four months, from Sept. 24, 2003 to Jan. 16, 2004.


4. How much viewing time was needed to make all the exposures?
The 800 exposures amounted to about 1 million seconds or 11.3 days of viewing time. The average exposure time was 21 minutes.


5. How many galaxies are in the image?

The image yields a rich harvest of about 10 000 galaxies.


6. How many colors (filters) were used to make the observations?
The colors used were blue, green, red, and near-infrared. The observations were taken in visible to near-infrared light.


7. If astronomers made the Hubble Ultra Deep Field observation over the entire sky, how long would it take?
The whole sky contains 12.7 million times more area than the Ultra Deep Field. To observe the entire sky would take almost 1 million years of uninterrupted observing.


8. How wide is the Ultra Deep Field's slice of the heavens?
The Hubble Ultra Deep Field is called a "pencil beam" survey because the observations encompass a narrow, yet "deep" piece of sky. Astronomers compare the Ultra Deep Field view to looking through an eight-foot-long soda straw.

The Ultra Deep Field's patch of sky is so tiny it would fit inside the largest impact basin that makes up the face on the Moon. Astronomers would need about 50 Ultra Deep Fields to cover the entire Moon.


9. How sharp is Hubble's resolution in pinpointing far-flung galaxies in the Ultra Deep Field?
Hubble's keen vision (0.085 arc seconds.) is equivalent to standing at the U.S. Capitol and seeing the date on a quarter a mile away at the Washington monument.

Image Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Explanation from: http://hubblesite.org/newscenter/archive/releases/2004/07/

Coronal Loops in an Active Region of the Sun

An active region of the sun just rotating into the view of NASA's Solar Dynamics Observatory gives a profile view of coronal loops over about a two-day period, from February 8-10, 2014. Coronal loops are found around sunspots and in active regions. These structures are associated with the closed magnetic field lines that connect magnetic regions on the solar surface. Many coronal loops last for days or weeks, but most change quite rapidly. This image was taken in extreme ultraviolet light.

Image Credit: NASA/Solar Dynamics Observatory
Explanation from: http://www.nasa.gov/content/coronal-loops-in-an-active-region-of-the-sun/

Aurora over Arjeplog

Arjeplog, Lapland, Sweden

Image Credit & Copyright: Maria Sundqvist

VST images the Lagoon Nebula

The VLT Survey Telescope (VST) at ESO's Paranal Observatory in Chile has captured this richly detailed new image of the Lagoon Nebula. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of eleven public surveys of the sky now in progress using ESO telescopes. Together these are providing a vast legacy of publicly available data for the global astronomical community.

Image Credit: ESO/VPHAS
Explanation from: http://www.eso.org/public/images/eso1403a/

Aurora over Tromsø

Tromsø, Norway

February 7, 2014

Image Credit & Copyright: Truls Tiller